This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to Swiss Patent Application No. 2000 1912/00 filed in Switzerland on Sep. 29, 2000; the entire content of which is hereby incorporated by reference.
Conventional spring scales with double tube technology have a non transparent outer tube with a slit with graduations along its sides. An inner tube with a protruding cam is inserted into an outer tube. The cam has marking functions while moving up and down in the graduation slit. This protruding cam may have frictions on the slit rims and thus may adulterate the measurement results. This protruding cam hinders the free rotation of the inner tube.
Through this slit impurities may get into the interior of the spring scale and can affect proper function.
The measurement graduation may only be read in the range of the slit.
Due to reasons of the measuring accuracy and stability such spring scales must almost conclusively have an outer tube made of metal, in particular made of aluminum. The manufacturing, the cutting of one or two threads, the printing and the colouring as well as the cutting of the slit on the outer tube are factors, which increase the price of the final product substantially.
The suspension clip or the hook attached to the spring scale for holding the weighing goods must be able to swivel freely, in order to avoid torsion and friction of the protruding cam in the slit of the outer tube. Such a mounting increases the price of the spring scale.
In conventional spring scales with double tube technology the set screw, as mentioned in the describing part of the independent claim, is screwed into a mounting support.
The regulating range of the spring bearing on the set screw can not be limited to one side, whereby it is possible that the set screw can be completely unscrewed from the spring bearing and thus the spring scale may completely lose its operability.
It is an object of the present invention to provide a spring scale which has no graduation slit in its outer tube and which has no corresponding protruding cam with marking function on its inner tube.
It is a further object of the present invention to provide a spring scale in which a spring holder and all elements connected to it in a non swivelling manner, with or without weighing goods attached, whereby the spring holder itself shall be freely swivellable, without hindering the zero point adjustment and the tare function.
It is a further object of the present invention to provide a spring scale in which the regulating range of a holder bearing on the set screw is limited on both sides.
This holder bearing shall have an inner thread and shall be, due to the presence of a spur, non swivellable and axially guided.
This spring scale shall have a closed outer tube which protects the inner technology from contamination.
It is a further object of the present invention to provide a spring scale with individual parts which are to be produced in an economic way and are easy to assemble.
It is a further object of the present invention to provide a spring scale which shall be precisely adjustable and shall be of easy and safe operation.
It is a further object of the present invention to provide a spring scale which is, by its construction, secured against involuntary disaggregation.
The cover and the outer tube of this spring scale shall in particular be connected to each other by means of gluing or welding in such a manner that non-destructive disaggregation is not possible.
The space provided for the spiral spring shall be dimensioned in such a way that a spiral spring with a favourable winding ratio may be used.
According to a preferred embodiment either the outer tube or the inner tube shall have imprinted or attached scales and inscriptions.
The outer tube shall especially be made of a material of low density and shall in its entirety be preparable in an easy, quick and low cost way.
The set screw shall especially rotate in an incremental way and thus be adjustable precisely and shall be protected against involuntary rotation.
With the present invention the above objects are achieved.
The present invention is defined in the independent claim.